Driving the common-mode of a Josephson parametric converter using a three-port power divider

ABSTRACT

An on-chip Josephson parametric converter is provided. The on-chip Josephson parametric converter includes a Josephson ring modulator. The on-chip Josephson parametric converter further includes a lossless power divider, coupled to the Josephson ring modulator, having a single input port and two output ports for receiving a pump drive signal via the single input port, splitting the pump drive signal symmetrically into two signals that are equal in amplitude and phase, and outputting each of the two signals from a respective one of the two output ports. The pump drive signal excites a common mode of the on-chip Josephson parametric converter.

BACKGROUND

Technical Field

The present invention relates generally to electronic devices and, inparticular, to driving the common-mode of a Josephson parametricconverter using a three-port power divider.

Description of the Related Art

A Josephson ring modulator (JRM) is a nonlinear dispersive element basedon Josephson tunnel junctions that can perform three-wave mixing ofmicrowave signals at the quantum limit. The JRM consists of JosephsonJunctions (JJs). In order to construct a non-degenerate parametricdevice that is the Josephson parametric converter (JPC), which iscapable of amplifying and/or mixing microwave signals at the quantumlimit, the JRM is coupled to two different microwave resonators.

In microstrip JPCs, as well as compact and shunted JPCs, the pump drivewhich provides the energy for the amplification process is fed throughthe sum port (Σ) of a 180 degree hybrid coupler. The difference port (Δ)of the same hybrid is used to feed the differential modes signal oridler tones to the JPC. In this configuration, both the pump and thesignal or idler are fed to the JPC through the same feedlines andcoupling capacitors of the JPC (to which the 180 degree hybrid coupleris connected).

In amplification, the pump frequency is at the sum of the idler andsignal frequencies and since the idler and signal frequencies areusually in the 4-15 Gigahertz range, the pump frequency is typicallyseveral Gigahertz apart from the signal and idler frequencies. Thus, inorder to feed both the pump and signal or idler tones through the samehybrid, the hybrid needs to be broadband enough to accommodate those twodifferent frequencies. For that purpose, existing JPCs use commercialbroadband hybrids which are big in size and are off chip. The additionof this bulky hardware limits scalability. To solve this problem, onecan design and implement broadband hybrids on-chip but this would addcomplexity to the design and fabrication processes. For example, if wecouple two JPCs on the same chip to form a quantum-limited Josephsondirectional amplifier, placing the hybrids in plane would require wirecross-overs.

Feeding the pump and the signal (or idler) tones to the JPC through thesame coupling capacitors poses a tradeoff between the device bandwidthand dynamic range. By increasing the coupling capacitors of theresonators, the device bandwidth increases since the coupling to thefeedline (i.e., external circuit) increases, but it also increases thecoupling to the second harmonic resonance of the microstrip resonatorwhich the pump tone (the common mode) is close in frequency to. Thissoftens the pump drive (makes it less “stiff”) and consequentlydecreases the dynamic range of the JPC.

SUMMARY

According to an aspect of the present principles, an on-chip Josephsonparametric converter is provided. The on-chip Josephson parametricconverter includes a Josephson ring modulator. The on-chip Josephsonparametric converter further includes a lossless power divider, coupledto the Josephson ring modulator, having a single input port and twooutput ports for receiving a pump drive signal via the single inputport, splitting the pump drive signal symmetrically into two signalsthat are equal in amplitude and phase, and outputting each of the twosignals from a respective one of the two output ports. The pump drivesignal excites a common mode of the on-chip Josephson parametricconverter.

According to another aspect of the present principles, a method isprovided. The method includes forming an on-chip Josephson parametricconverter. The forming step includes forming a Josephson ring modulator.The forming step further includes forming a lossless power divider,capacitively coupled to the Josephson ring modulator, having a singleinput port and two output ports for receiving a pump drive signal viathe single input port, splitting the pump drive signal symmetricallyinto two signals that are equal in amplitude and phase, and outputtingeach of the two signals from a respective one of the two output ports.The pump drive signal excites a common mode of the on-chip Josephsonparametric converter.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows an exemplary circuit for a Josephson Parametric Converter(JPC) 100 having a common-mode driven using a power divider, inaccordance with an embodiment of the present principles;

FIG. 2 an exemplary implementation layout for the Josephson ParametricConverter (JPC) 100 of FIG. 1, in accordance with an embodiment of thepresent principles;

FIG. 3 shows a three-port power divider circuit 300, in accordance withan embodiment of the present principles;

FIG. 4 shows another three-port power divider circuit 400, in accordancewith an embodiment of the present principles; and

FIG. 5 shows an exemplary method 500 for forming a Josephson ParametricConverter (JPC) 100 having a common-mode driven using a three-port powerdivider, in accordance with an embodiment of the present principles.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present principles are directed to driving the common-mode of aJosephson Parametric Converter (JPC) using a three-port power divider.

In the JPC, the incoming and outgoing signals to (in) and from (out) ofthe device travel on the same transmission lines and feedlines.

In an embodiment, we couple the pump drive and the signal (or idler)tones to the JPC using separate feedlines and coupling capacitors. Thesignal and idler tones would continue to be fed through the couplingcapacitors of the JPC resonators, but the pump drive would be fed to theJPC through a lossless on-chip three-port power divider capacitivelycoupled to the Josephson ring modulator (JRM) of the JPC. The powerdivider would split the input signal equally between the two outputports and the split signals would have equal phase (in order to excitethe common mode).

The present principles provide many attendant advantages over the priorart. Some of these many attendant advantages will now be described.

As an advantage, hybrid couplers are not needed for feeding or drivingthe JPC. The new excitation method yields a smaller footprint andinvolves a simpler design and fabrication processes. Obviously, it isadvantageous not to use hybrids at all because they might require wirecross-overs but if for some reason it is not an issue (due to the use ofadvanced and reliable fabrication process), the main advantage is thatthe pump drive does not need to share a hybrid or physical port with theinput and output signals. Also, in the case that hybrids are used, thehybrids do not need to be broadband covering a large bandwidth(usually >10 GHz).

As another advantage, the power divider can be implemented on chip andit is lossless. It does not need to be broadband. Also, capacitivelycoupling the power divider to the JRM allows us to strongly couple tothe common-mode of the JPC, which we want to drive (i.e., the pump), andat the same time weakly couple to the differential modes, which we wantto preserve (i.e., the signal and idler). This last statement isespecially true in microstrip JPCs where the odd Eigenmodes of theresonators have an RF-voltage node at the JRM location, whereas the evenEigenmodes of the resonators have an RF-voltage anti-node at the JRMlocation.

As yet another advantage, the pump, signal, and idler tones can be fedto the JPC through different feedlines which can be implemented atseparate physical locations on chip, thus facilitating integration withother JPCs.

As still another advantage, the dynamic range of microstrip JPCs can beincreased by making the pump drive stiffer without affecting the devicebandwidth. This can be achieved by, for example, decreasing the couplingcapacitors to the JRM and also incorporating microwave filters into thefeedlines of the resonators which block the pump drive from leaking outthrough these feedlines.

FIG. 1 shows an exemplary circuit for a Josephson Parametric Converter(JPC) 100 having a common-mode driven using a power divider, inaccordance with an embodiment of the present principles.

The JPC 100 includes a Josephson ring modulator (JRM) 110. The JRM 110includes four nodes 101, 102, 103, and 104. The JRM 110 further includesJosephson junctions 111A, 111B, 111C, and 111D arranged in a WheatstoneBridge-like configuration with respect to the four nodes 101-104 (thatis, in a ring configuration with the nodes 101-104 inter-dispersedbetween the junctions 111A-111D), where junction 111A is between nodes101 and 102, junction 111B is between nodes 102 and 103, junction 111Cis between nodes 103 and 104, and junction 111D is between nodes 104 and101. The Josephson junctions 111A-D form a superconducting loop threadedby an applied magnetic flux Φ. In an embodiment, the flux bias appliedto the ring is half a flux-quantum. Of course, other amounts can also beused, depending upon the application. In particular, if a flux-tunableversion of the JRM is implemented where each JJ in the JRM is shunted bya linear inductance.

The JPC 100 also includes 2 transmission line resonators that intersectat the JRM 110, namely, a signal (S) resonator which include twotransmission lines 171 and 161 of length l_(s)/2 each, connectedtogether by the JRM, and an idler resonator (I) which include twotransmission lines 172 and 162 of length l_(i)/2 each connected togetherby the JRM. The signal (S) resonator is excited by a signal (S) tone,while the idler (I) resonator is excited by an idler (I) tone. “Signal(S)” is interchangeably denoted herein as “signal 1”, while idler (I) isinterchangeably denoted herein as “signal 2”. The respective lengths ofthe signal (S) and the idler (I) transmission line resonators and theJosephson inductance of the JRM 110 at the device working point (i.e.,the flux bias threading the JRM loop) determine the resonancefrequencies of the JPC 100. In general, l_(s)≈λ_(s)/2 and l_(i)≈λ_(i)/2,where λ_(s) and λ_(i) correspond to the wavelength of the fundamentalmode of the S and I resonators respectively. The signal (S) resonatorand the idler (I) resonator support a different one of two differentialEigenmodes of the JRM 110.

The (differential) signal (S) tone is fed to nodes 101 and 103 of theJRM 100 through feedline 151 via a coupling capacitor 131. The(differential) idler (I) tone is fed to nodes 102 and 104 of the JRM 100through feedline 152 via a coupling capacitor 132. A third tone, denotedas pump (P), is non-resonant and is input to nodes 101 and 103 of theJRM 110 via a lossless on-chip power divider 199 capacitively coupled tothe JRM 110 via coupling capacitors 133A and 133B. Both the signal (S)Eigenmode and the idler (I) Eigenmode are excited differentially, whilethe pump (P) is a common-mode drive. The linear bandwidth of the signal(S) resonator and idler resonator (I) is mainly set by the couplingcapacitors which couple the signal (S) resonator and idler resonator (I)to the respective feedlines. Thus, the signal (S) and the idler (I)tones, which lie within the bandwidths of the signal (S) resonator andidler resonator (I), couple to the differential modes of the JRM 110,while the pump (P) drive couples to the common-mode of the JRM 110.Denoting the frequency of the signal (S) tone f_(S), the frequency ofthe idler (I) tone f_(I), and assuming, without loss of generality, thatf_(I)>f_(S), the frequency of the pump drive f_(P) is set to either thesum f_(I)+f_(S) (amplification) or the difference f_(I)−f_(S) (frequencyconversion without photon gain).

It is to be appreciated that one of more embodiments here describe aspecific implementation of a JPC in which the resonators includedtherein are realized using transmission line resonators. However, thepresent principles are not limited to this particular implementationand, thus, JPCs having other elements and/or other configurations canalso be used in accordance with the teachings of the present principles,while maintaining the spirit of the present principles. For example, inother embodiments, the resonators can be implemented usinglumped-elements. The preceding also applies to the JRM in that thepresent principles are not limited to the specific JRM configurationshown herein.

FIG. 2 an exemplary implementation layout for a Josephson ParametricConverter (JPC) 200 having a common-mode driven using a power divider,in accordance with an embodiment of the present principles.

The JPC 100 includes a dielectric substrate 210 on which the JRM 110 isdisposed. The JPC 100 also includes two microstrip resonators thatintersect at the JRM 110, namely, the signal (S) resonator whichincludes two microstrip lines 171 and 161, each connected together bythe JRM 110, and the idler resonator (I) which includes two microstriplines 172 and 162, each connected together by the JRM 110. As notedabove, signal (S)” is interchangeably denoted herein as “signal 1”,while idler (I) is interchangeably denoted herein as “signal 2”.

The JPC 110 includes a three-port power divider 210 having an input port201, and two output ports 202 and 203 which are capacitively coupled tothe JRM 110 via capacitors 133A and 133B. Feedline 151 is the feedlinefor signal 1, and feedline 152 is the feedline for signal 2.

Capacitor 131 couples the Signal (S) tone to the JRM 110, capacitor 132couples the Idler (I) tone to the JRM 110, and capacitors 133A and 133Bcouple the pump (P) drive tone to the JRM 110.

FIGS. 3 and 4 herein after show respective three-port power dividercircuits in accordance with embodiments of the present principles. It isto be appreciated that the present principles are not limited to solelythe power divider circuits shown in FIGS. 3 and 4, and other powerdivider circuits, as well as modified versions of those shown in FIGS. 3and 4, can be used in accordance with the teachings of the presentprinciples, while maintaining the spirit of the present principles.

FIG. 3 shows an exemplary three-port power divider circuit 300, inaccordance with an embodiment of the present principles.

The power divider circuit 300 shows a transmission line model of thedivider. The power divider circuit is a lossless variation of the lossyWilkinson power divider. The divider includes three sections. The firstsection includes an input line of characteristic impedance Z₀. Thesecond section includes a junction in which the input line is split intotwo transmission lines of characteristic impedance √2Z₀ and lengthλ_(P)/4, where λ_(P) is the wavelength of the pump drive. The thirdsection includes two transmission lines of characteristic impedance Z₀.This divider has three ports 301-303. Port 301 is defined on the inputline. Ports 302 and 303 are defined on the output lines. This dividerfunctions as a 3 dB divider. A pump drive at wavelength λ_(P) and powerP_(P) input on port 301 is divided into two equal signals which aretransmitted to ports 302 and 303. Due to the symmetry of the structurethe output signals on ports 302 and 303 will have equal phases. Thus,the first port 301 of characteristic impedance Z₀ receives a pump tonehaving a wavelength of λ_(P) and power P_(p). The second port 302 andthird port 303 of characteristic impedance Z₀ output respectivepower-divided pump signals with power P_(p)/2 and equal microwave phasedue to the symmetry of the structure. In an embodiment, the three-portpower divider consists of two quarter wave transmission lines (of lengthλ/4) and characteristic impedance √2Z₀ which connect between port 301and ports 302-303. The input line in this divider is matched if theoutput lines are matched. However, matching the input line is lesscritical for the pump drive. Also, in this divider there is no isolationbetween the output lines, however the symmetry of the divider ensuresthat the steady state phases of the driven signals on the output portsare equal. In an embodiment, the power divider circuit 300 can be alsoimplemented by an equivalent lumped-element circuit.

FIG. 4 shows exemplary another three-port power divider circuit 400, inaccordance with an embodiment of the present principles.

The power divider circuit 400 includes a first port 401, a second port402, and a third port 403. This power divider is known as losslessT-junction based on transmission lines. The three ports are defined onthree transmission lines, i.e. input line and two output lines. Port 401is defined on the input line, ports 402 and 403 are defined on theoutput lines. The characteristic impedance of the input line is Z₀,while the impedance of the two output lines is 2Z₀. This choice ofcharacteristic impedances implements a 3 dB power divider, where a pumpdrive entering port 401 at frequency f_(p) is split in half. Half of thepower is delivered to port 402 and the other half to port 403. Due tosymmetry, the split signals on both ports have the same phase. Ifnecessary, quarter-wave transformers can be used to bring the outputline impedances to a different desired value. It is important to notethat in this divider the input line is matched if the output lines arematched. However, matching the input line is less critical for the pumpdrive. Also, in this divider there is no isolation between the outputlines, however the symmetry of the divider ensures that the steady statephases of the driven signals on the output ports are equal. In anembodiment, the power divider circuit 400 is implemented by anequivalent lumped-element circuit.

In the embodiments of FIGS. 3 and 4, the power dividers 300 and 400 arereciprocal devices, meaning that the transmission from one port toanother is the same in both directions. One important consequence of thedevice having three ports and being lossless and reciprocal is that itcannot be matched on all ports. Matched means that power sent into oneport will not have some portion of it reflected back. In the proposeddevice, matching is less important.

In an embodiment, a microwave filter is added to the power divideritself (possibly to both port 2 and 3 or to port 1), in order to blockany possible signal leakage from the JPC through the power divider.

FIG. 5 shows an exemplary method 500 for forming a Josephson ParametricConverter (JPC) 100 having a common-mode driven using a three-port powerdivider, in accordance with an embodiment of the present principles. Itis to be appreciated that one or more steps have been omitted frommethod 500 for the sake of brevity, but are readily apparent to one ofordinary skill in the art given the teachings of the present principlesprovided herein.

At step 510, form a Josephson ring modulator having four nodes and atleast Josephson junction arranged in between every two consecutive onesof the four nodes in a ring configuration.

At step 520, form a first and a second resonator that couple to theJosephson ring modulator and respectively enable a first and a secondEigenmode of the on-chip Josephson parametric converter.

At step 530, form a lossless power divider, coupled to the Josephsonring modulator, having a single input port and two output ports forreceiving a pump drive signal via the single input port, split the pumpdrive signal symmetrically into two signals of equal phase andamplitude, and output each of the two signals from a respective one ofthe two output ports. The pump drive couples to the common mode of theJRM. In an embodiment, the lossless power divider is formed to includeat least one microwave filter at the single input port or one or bothoutput ports, in order to block any possible signal leakage from the JPCthrough the power divider.

At step 540, form one or two feedlines for receiving a first modesignal, one or two additional feedlines for receiving a second modesignal, and a feedline for receiving the pump drive. In an embodiment,the feedlines are formed at different chip locations. In an embodiment,the feedlines for exciting the first mode signal are coupled to thefirst resonator through coupling capacitors. Likewise, the feedlines forexciting the second mode signal are coupled to the second resonatorthrough coupling capacitors.

In an embodiment, the feedlines for exciting the first mode signal canbe formed to include a microwave filter for filtering signals at thepump frequency and/or the second harmonic resonance frequency of thefirst resonator, and the feedlines for exciting the second mode signalcan be formed to include a microwave filter for filtering signals at thepump frequency and/or the second harmonic resonance frequency of thesecond resonator. The preceding technique can be used to increase thebandwidth of a microstrip-implemented JPC by increasing the couplingbetween the fundamental modes of the JPC resonators and the feedlineswithout increasing the coupling between the second harmonic resonancesof the JPC and the feedlines which can result in a decrease in thestiffness of the pump when the device is used as a phase-preservingamplifier.

In an embodiment, the feedlines are formed to include a couplingcapacitor for coupling a respective one of the feedlines to theJosephson ring modulator.

A description will now be given regarding some exemplary applications towhich the present principles can be applied.

The present principles can be used in the readout of solid state qubitssuch as superconducting qubits and quantum dots. For example, thepresent principles can be used to enhance the measurement fidelity, andallow for scalable readout architectures. The present principles canalso be used, in general, to perform sensitive quantum measurements inthe microwave domain, such as measuring nanomechanical systems coupledto microwave resonators.

The present principles can be used in building wideband, large inputpower quantum-limited Josephson directional amplifiers and also on-chipdissipationless circulators. The present principles can be used (similarto Josephson parametric converters but with enhanced performance) asideal microwave mixers (performing upconversion and downconversion ofmicrowave frequency without dissipation), controllable microwavebeam-splitters, and fast, lossless microwave switches.

The present principles can also find some applications in improving thesensitivity of microwave measurements in the areas of astronomy andcosmology.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. An on-chip Josephson parametric converter,comprising: a Josephson ring modulator; and a lossless power divider,coupled to the Josephson ring modulator, having a single input port andtwo output ports for receiving a pump drive signal via the single inputport, splitting the pump drive signal symmetrically into two signalsthat are equal in amplitude and phase, and outputting each of the twosignals from a respective one of the two output ports, wherein the pumpdrive signal excites a common mode of the on-chip Josephson parametricconverter, and wherein the lossless power divider comprises at least onemicrowave filter for at least mitigating any signal leakage from theon-chip Josephson parametric converter through the lossless powerdivider.
 2. The on-chip Josephson parametric converter of claim 1,further comprising one or more coupling capacitors for capacitivelycoupling the lossless power divider to the Josephson ring modulator. 3.The on-chip Josephson parametric converter of claim 1, furthercomprising a plurality of feedlines for receiving a first mode signal,and a second mode signal, and the pump drive signal.
 4. The on-chipJosephson parametric converter of claim 3, wherein at least some of theplurality of feedlines are disposed at different on-chip locations. 5.The on-chip Josephson parametric converter of claim 3, furthercomprising a first resonator and a second resonator that intersect atthe Josephson ring modulator and respectively enable a first and asecond differential mode of the on-chip Josephson parametric converter,and wherein at least some of the plurality of feedlines are connected tothe first and second resonators and comprise a respective microwavefilter for filtering microwave signals at at least one of a pumpfrequency and second harmonic resonance frequencies of the first andsecond resonators.
 6. The on-chip Josephson parametric converter ofclaim 3, further comprising respective coupling capacitors for couplingrespective ones of the at least some of the plurality of feedlines tothe Josephson ring modulator.
 7. The on-chip Josephson parametricconverter of claim 1, wherein the lossless power divider is a passivedevice consisting of one or more passive elements.
 8. The on-chipJosephson parametric converter of claim 1, wherein the lossless powerdivider comprises a three port passive element.
 9. The on-chip Josephsonparametric converter of claim 1, wherein the lossless power dividercomprises lumped-circuit elements.
 10. The on-chip Josephson parametricconverter of claim 1, further comprising transmission lines andfeedlines, wherein the incoming signals to and outgoing signals from thelossless power divider travel on same ones of the transmission lines andsame ones of the feedlines.
 11. The on-chip Josephson parametricconverter of claim 1, wherein the at least one microwave filter isprovided at the single input port or at one or both of the two outputports of the lossless power divider.
 12. A method, comprising: formingan on-chip Josephson parametric converter, wherein said forming stepincludes: forming a Josephson ring modulator; and forming a losslesspower divider, capacitively coupled to the Josephson ring modulator,having a single input port and two output ports for receiving a pumpdrive signal via the single input port, splitting the pump drive signalsymmetrically into two equal phase signals, and outputting each of thetwo equal phase signals from a respective one of the two output ports,wherein the pump drive signal excites a third mode that is a common modeof the on-chip Josephson parametric converter, and wherein the losslesspower divider is formed to include at least one microwave filter for atleast mitigating any signal leakage from the on-chip Josephsonparametric converter through the lossless power divider.
 13. The methodof claim 12, further comprising forming a coupling capacitor forcapacitively coupling the lossless power divider to the Josephson ringmodulator.
 14. The method of claim 12, further comprising forming aplurality of feedlines, each for respectively carrying incoming andoutgoing waves of a first mode signal, and a second mode signal, and thepump signal.
 15. The method of claim 14, further comprising: forming afirst and a second resonator that intersect at the Josephson ringmodulator and respectively enable a first and a second mode of theon-chip Josephson parametric converter; and connecting at least some ofthe plurality of feedlines to the first and second resonators, andwherein forming a plurality of feedlines comprises forming a respectivemicrowave filter in each of the at least some of the plurality offeedlines for filtering microwave signals at the pump frequency and/orthe respective second harmonic resonance frequencies of the first andsecond resonators.
 16. The method of claim 12, wherein the losslesspower divider is formed as a passive device consisting of one or morepassive elements.
 17. The method of claim 12, wherein the lossless powerdivider is formed using lumped-circuit elements.
 18. The method of claim12, further comprising: forming transmission lines and feedlines; andconfiguring the on-chip Josephson parametric converter to operate suchthat incoming signals to and outgoing signals from the on-chip Josephsonparametric converter travel on same ones of the transmission lines andsame ones of the feedlines.